The present invention relates to doors and more particularly to overhead doors which are employed in industrial application including mining application.
It is known to construct an industrial door structure which includes a curtain for closing the doorway and a curtain winding mechanism for raising and lowering the curtain. Such a door structure is disclosed in South African Pat. No. 80/0440 wherein the inventor is Glenn R. Palmer. This known door is advantageous in that damage is minimal if the door is struck by a vehicle which must pass through the door on a regular basis. The curtain is made of a rubber composition and it is thicker along its side edges so that it is normally retained at the side edges in guide channels. In many mining applications, there is often a pressure differential on opposing sides of the door and the edges of the curtain are designed to sealingly engage the guide channels in order to maintain the pressure differential.
In applications where doors, including flexible curtain doors, have to be maintained closed to maintain a predetermined pressure within an environment, experience has shown that differential pressure building up on opposing sides of the door can make it extremely difficult if not impossible, to open the door.
It is an object of the present invention to provide a pressure-differential compensating door which can be readily opened when different pressures exist on opposing sides of the door.
It is a further object of the present invention to provide a pressure-differential compensating door which is also a damage-minimizing door which can be readily repaired and maintained subsequent to an impact with vehicular traffic.